Climate change not responsible for rising alcohol levels: study

A recent US report has cast doubt on winemakers' claims that climate change is responsible for increased alcohol content.

American Association of Wine Economists

A recent US report has cast doubt on winemakers’ claims that climate change is responsible for increased alcohol content.

The report, ‘Splendide Mendax – False Label Claims about High and Rising Alcohol Content in Wine’ from the American Association of Wine Economists, analysed climate data from1992-2009.

This comprised 129,123 samples of wines, including 80,421 red wines and 46,985 white wines from all around the world.

It found that the heat index in most wine-making countries grew less than the rise in alcohol, and could not be attributed as the major factor driving the steady increase.

The heat index was created by averaging the daily high and low temperatures over the relevant growing season in the various countries sampled.

The research indicates, the authors say, that the average alcohol content in wine has increased by 1.12% over 18 years, from a mean of 12.7%.’

This, they say, is considerably higher than would be expected when set against the heat index, which predicts an average rise of 0.05% in alcohol per year.

‘It would take a whopping 20 degree Fahrenheit (6.67 Celsius) increase in the average temperature in the growing season to account for a 1 percentage point increase in the average alcohol content of wine.

The study also found discrepancies between alcohol content stated on labels and actual content in bottle. In 57% of the 100,000 samples the alcohol level was understated with the worst offending being New World red wine, which averaged 0.45 percentage points below the stated level.

Lead author Julian Alston of UC Davis cited other factors such as evolving market preferences as key contributors.

But laid the responsibility with winemakers: ‘Label claims appear to be biased towards a perceived norm, a desired alcohol percentage to report for a particular wine – red or white.

‘It may be profitable for the winery to give the consumer both the desired wine characteristics (including higher actual alcohol content) and the desired label characteristic, by understating the true alcohol content. This parable is consistent with explanations we have been given by some winemakers.’

Alston also pointed out that tax rates were a powerful inducement to distort alcohol information: Federal Wine Excise Tax is US$1.07 per gallon for wine of 14% alcohol or less, and US$1.57 per gallon for 14.1% to 21% alcohol.

As regards the reasons for the actual rise in alcohol around the world, the authors suggest there may be many climatological or cultural factors that have not been measured, but ‘our findings lead us to think that the rise in alcohol content of wine is primarily man-made.’